Aqueous polymeric thickening agents

ABSTRACT

A novel polymer of a vinyl benzyl ether monomer and at least one other copolymerizable monomer, at least one of which other monomers has a carboxylic acid group, an anhydride group, a sulfate group, a sulfonate group or a hydroxyl group is disclosed. The vinyl benzyl ether monomer has the formula ##STR1## wherein R is hydrogen or methyl, m is about 10 to 100 and Y is --OR 1 , --SR 1 , ##STR2## where R 1  is an alkyl, aralkyl or alkaryl hydrophobic group of 10 to about 22 carbon atoms, R 2  is an alkyl group of 1 to about 22 carbon atoms and R 3  is hydrogen or an alkyl group of 1 to about 22 carbon atoms, provided R 2  and R 3  in combination have at least 10 carbon atoms.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division, of application Ser. No. 267,570 filed June 29, 1972,now U.S. Pat. No. 4,008,202.

BACKGROUND OF THE INVENTION

Polymeric water soluble thickening agents are widely used for manypurposes and many such agents of different chemical types arecommercially available. The diversity of available products is anindicator that they are not all equally useful. It is not unusual tofind some thickening agents which perform well in a certain environmentand not at all in another environment. In fact, in some uses no onethickening agent is completely satisfactory and there is a continualneed and a continuing search for new thickening agents to satisfy manyof the unmet needs. Latex paint thickening is a good example, where themarket is actively seeking an agent which will provide stable thickeningas well as other properties such as flow and leveling.

U.S. Pat. Nos. 2,921,930 and 3,301,829 propose to make thickening agentsby esterification of anhydride containing polymers. While certain ofthese polymeric esters provide thickening power, the viscosity of theaqueous system is not stable to storage. U.S. Pat. No. 3,499,876proposes to make water soluble thickening agents from certain monomers.While no information is available therein to judge storage stability, aprincipal problem is the limited range of monomers which can becopolymerized together.

It is an object of this invention to provide aqueous storage stablethickening agents which may be prepared from a variety of monomers.

SUMMARY OF THE INVENTION

Essential to the preparation of the copolymers of this invention is avinyl benzyl ether monomer having the formula ##STR3## wherein R ishydrogen or methyl, m is about 10 to 100 and Y is --OR₁, --SR₁, ##STR4##where R₁ is an alkyl, aralkyl or alkaryl hydrophobic group of 10 toabout 22 carbon atoms, R₂ is an alkyl group of 1 to about 22 carbonatoms and R₃ is hydrogen or an alkyl group of 1 to about 22 carbonatoms, provided R₂ and R₃ in combination have at least 10 carbon atoms.

Copolymers are prepared to contain in polymerized form about 0.2 to 15mole percent of said vinyl benzyl ether and the balance to make 100percent of at least one other copolymerizable monomer provided that awater solubilizing amount of one or more monomers having a carboxylicacid group, an anhydride group, a sulfate group, a sulfonate group or ahydroxyl group is employed in the preparation of the compolymer.

DESCRIPTION OF THE INVENTION

The copolymers of this invention require certain amounts of the vinylbenzyl ether monomer to impart the beneficial thickening effect and awater solubilizing amount of a monomer having water solubilizing groups.Optionally the copolymers can be prepared to contain most any othercopolymerizable monomer or mixture of same provided the two requiredtypes of monomers are employed.

By water solubilizing groups it is meant to include groups which providethe copolymer with sufficient hydrophilic properties as to be directlysoluble in water or soluble in water as a neutralized salt of a basesuch as ammonia, alkali metal bases (NaOH, LiOH, KOH, NaHCO₃, K₂ CO₃ andthe like), alkyl amines and the like. Said groups include carboxylicacids, anhydrides, sulfates, sulfonates and hydroxyl. Carboxylic acids,sulfates and sulfonates readily form salts of the above bases.Anhydrides readily hydrolyze in water to the dicarboxylic acid which maybe neutralized with said bases. In addition, anhydrides react withammonia to form the half amide/half acid which can be furtherneutralized with ammonia to the half amide/half ammonium salt or withany of the above bases. Mono-primary and -secondary amines reactsimilarly to ammonia. Tertiary monoamines may also be used to hydrolyzeand neutralize the anhydride group except that a half amide will not beformed. Generally, polyfunctional amines should be avoided sincecrosslinking may result with the anhydride group, but in certaininstances polyfunctional amines may provide beneficial propertiesespecially if used in small amounts in conjunction with another of saidbases.

By water solubilizing amount of said monomer it is meant at least theminimum amount necessary to make the copolymer water soluble or readilydispersible in an aqueous system. The specific amount will vary quitewidely depending on the choice of the vinyl benzyl ether, the watersolubilizing monomer (i.e. the particular water solubilizing group) andof any optional additional monomers, but can be readily determined by askilled worker based on the known properties of the monomers and withroutine evaluation.

Vinyl benzyl ether monomers have the formula ##STR5## where R, m and Yare as previously described. While the number of oxyalkylene groups##STR6## may vary from 10 to about 100, preferably the number ofoxyalkylene groups is at least 20 to 40. The oxyalkylene groups may be amixture of oxyethylene and oxypropylene groups, either heteric or block,but it is preferred that all such groups be oxyethylene groups.

The nature of the linking groups between the oxyalkylene chain and thehydrophobic group are not considered significant, since they are allhydrophilic groups. The linking group is more dependent merely on thereactants employed to provide the hydrophobic group. An ethoxylatedfatty acid introduces the ##STR7## an ethoxylated nonyl phenol or fattyalcohol the --O-- group, an ethoxylated mercaptan the --S-- group, anethoxylated fatty amide the ##STR8## or an ethoxylated fatty amine the##STR9## Nonionic surfactants of the above type and their preparationare fully described in "Nonionic Surfactants," Vol. 1, edited by M. J.Schick, published by Marcel Decker, Inc., New York, 1967.

R₁ may be an alkyl, aralkyl or alkaryl hydrophobic group having from 10to 22 carbon atoms. Typical R₁ groups include lauryl, myristyl, cetyl,stearyl, oleyl, linoleyl, 2-phenyl decyl, octyl phenyl, decyl phenyl,dodecyl phenyl and the like. The R₁ groups are normally provided by thealkoxylated derivatives of alkyl phenols, fatty acids, fatty amides,fatty mercaptans, fatty alcohols or fatty amines which are reacted withvinyl benzyl chloride (or bromide) to prepare the monomer. R₂ includesmethyl, ethyl butyl and like groups including those alkyl groups withinthe definition of R₁, above. R₃ is similar to R₂.

Preferably the vinyl benzyl ether monomer comprises from about 0.2 to 5mole percent of the polymer and more preferably about 1 to 3 molepercent.

The vinyl benzyl ether monomers may be prepared according to theprocedure described in U.S. Pat. No. 3,190,925. It is preferable toemploy in the reaction alkoxylated hydrophobic materials which havelittle or no diol content to avoid formation of divinyl or polyvinylmonomers. The diol content may be minimized or eliminated by removingall traces of water from the reactants, solvents, etc. used in thecondensation of the alkylene oxide with the hydrophobe (e.g.ethoxylation of nonyl phenol) and by preventing water of formation byusing sodium metal as the catalyst in place of sodium hydroxide.

EXAMPLE 1 Preparation of a Vinyl Benzyl Ether Monomer.

Into a nitrogen purged stainless steel kettle was charged 1512 gms(0.727 mole) of an ethylene oxide condensation product of nonyl phenolhaving an average value for m of about 40 (nonyl phenol/40 EO), 2415 gmsof t-butyl alcohol as a solvent and 16.4 gms of sodium metal (0.715mole). The contents of the kettle were heated at 100° C for 2 hourswhile the pressure rose from 0 to 50 psig and then leveled off. Aftercooling to room temperature, 107 gms of vinyl benzyl chloride (0.702mole) was added, the kettle purged with nitrogen and the contents heatedat 50°-65° C. After 3 3/4 hours a base titration showed 94% conversionto the vinyl benzyl ether monomer. The contents were allowed to reactfor an additional 2 hours at 50°-55° C and then neutralized to pH 6-7with 2.85 gms of 95% acetic acid.

The alcohol solvent was removed by distillation until the kettletemperature was 80° C and the pressure 20 mm Hg. One gallon of benzenewas added and then 1 quart distilled off to remove traces of alcohol.The slurry was filtered at 175 mm Hg and 50° C to remove NaCl and sodiumacetate salts. The remaining benzene was removed by distillation at 80°C and 20 mm Hg. The waxy solid product had a melting point of 35°-40° Cand weighed 1530 gms. Bromide/bromate titration in methanol gave anequivalent weight of 2180 gms/mole of unsaturation.

t-Butyl alcohol is a preferred solvent because it results in goodreaction rates and yields. The reaction should be maintained below about65° C to prevent polymerization in the strongly basic medium. Since thesalts are partially soluble in the alcohol, it is replaced by benzeneprior to filtration. The salts are undesirable because they aredetrimental to polymerization. Benzene is a preferred recovery solventbecause it dissolves the product, doesn't dissolve the salts and is lowboiling and readily removed.

Following the procedure of example 1, vinyl benzyl ether monomers wereprepared in which R was hydrogen, Y was --OR₁ and R₁ and m were asfollows.

    ______________________________________                                        R.sub.1                 m                                                     ______________________________________                                        A      n-decyl              40                                                B      n-dodecyl            40                                                C      n-octadecyl           7                                                D       "                   20                                                E       "                   40                                                F      nonyl phenyl         10                                                G       "                   20                                                H       "                   40                                                ______________________________________                                    

Water solubilizing monomers include acrylic acid, methacrylic acid andthe like; sodium styrene sulfonate, sulfoethyl methacrylate ##STR10##hydroxyalkyl acrylates and methacrylates wherein the alkyl grouppreferably has from 2-4 carbon atoms but may have more; dicarboxylicacids or their anhydrides such as maleic anhydride, itaconic anhydride,citraconic anhydride, chloromaleic anhydride, fumaric acid, maleic acid,itaconic acid and the like or the half ester or half amides of saidacids. Monomers such as vinyl acetate may be used since the polymer maybe hydrolyzed to produce the alchohol group.

Copolymerizable monomers which may be optionally used include alkenylaromatic monomers, olefinic monomers, diesters of unsaturateddicarboxylic acids, vinyl ethers, vinyl esters, alkyl esters of acrylicand methacrylic acid and the like. Typical of such monomers are α-methylstyrene, vinyl toluene, ethylene, propylene, vinyl methyl ether, vinylethyl ether, vinyl acetate, vinyl benzoate, ethyl acrylate, methylmethacrylate, cyclohexyl acrylate, 2-ethyl hexyl methacrylate, diethylmaleate, dibutyl fumarate and the like. Certain monomers having reactivegroups which might interact with the water solubilizing groups should beavoided. A skilled worker would know to do that.

The copolymers of this invention by virtue of the presence of the vinylbenzyl ether monomers already described are excellent thickening agentswhich are storage stable in contrast to many other available thickenerssuch as the esters of anhydride copolymers. Consequently, they areuseful in thickening latex paints, in drilling muds, as thickeners insecondary oil recovery, gelling agents for cosmetics and the like.

The invention may be further illustrated, but not limited to, by thefollowing examples which show the preparation of a terpolymer ofstyrene, maleic anhydride and the vinyl benzyl ether of nonylphenoxy(ethyleneoxy)₄₀ ethanol (abbreviated as nonyl phenol/40 EO).

EXAMPLE 2

In a 500 ml flask equipped with mechanical agitation, a condenser,thermometer, N₂ inlet tube and an external heating bath was added 100 mlof toluene, 9.8 gms (0.1 mole) maleic anhydride and 11.3 gms (0.005mole) of vinyl benzyl ether of nonyl phenol/40 EO (eq. wt. per doublebond, 2260). The mixture was stirred to form a clear solution. Then 9.88gm (0.095 mole) of styrene and 0.0098 gm of azobisisobutyronitrilecatalyst was added. The polymerization was conducted at 90° C for 3hours. Onset of polymerization was indicated by an initial slightdevelopment of turbidity at 88° C. The resulting product was a slightlyviscous translucent dispersion. The mixture was cooled and devolatilizedunder vacuum at 80° C to remove the solvent. Polymer product yield was31.58 gms. The polymer had an inherent viscosity in acetone at 25° C of0.41 and a 10% solution viscosity in methyl ethyl ketone (MEK) at 25° Cof 6.36 cps.

A 5% sodium salt solution of the polymer was made by dispersing it inwater and neutralizing with NaOH (1.75 moles NaOH/mole of anhydride).The clear solution had a Brookfield viscosity of 7700 cps (#5 spindle,20 rpm. 25° C).

EXAMPLE 3

Example 2 was repeated except the solvent was replaced by 67 gms of MEK.The solution of monomers and catalysts was heated at 80° C for 4 hourswith stirring in a N₂ atmosphere. A clear viscous solution was producedwhich was devolatilized under vacuum at 80° C. Recovered polymer weightwas 30.87 gms; inherent viscosity -- 0.337; solution viscosity -- 3.06cps and a 5% sodium salt solution had a Brookfield viscosity of 4500cps.

EXAMPLE 4

Copolymers similar to example 2 and 3 were made at varying conditions ofpolymerizations. The monomers and catalyst were the same as previouslyused and viscosities determined as before. The results are reported inTable I.

                                      TABLE I                                     __________________________________________________________________________                                                    5% Na Salt                          Monomers       Vazo Temp. of                                                                            Yield*          of polymer                    S     MA    VBE Solvent                                                                            catalyst                                                                           polymer-                                                                            of       .sup.η 10%                                                                       soln. Vis-                    grams grams grams                                                                             grams                                                                              grams                                                                              ization                                                                             polymer                                                                            .sup.η inh                                                                    cps    cosity-cps                    __________________________________________________________________________    a)                                                                              9.88                                                                              9.8   10.8                                                                              Toluene                                                                            0.05 110°/3 hrs                                                                   29.59                                                                              0.238                                                                             2.89   1200                                          100                                                           b)                                                                              9.88                                                                              9.8   11.65                                                                             MEK  0.098                                                                               30°/4 hrs                                                                   30.85                                                                              0.29                                                                              2.3    1240                                          114.4                                                         c)                                                                              9.88                                                                              9.8   11.65                                                                             67   0.098                                                                               80°/4 hrs                                                                   30.87                                                                              0.337                                                                             3.06   4500                          d)                                                                              9.8 9.8   10  Toluene                                                                            0.1  105°/3 hrs                                                                   31.2 --  --     2700                                          100                                                           d)                                                                              9.88                                                                              9.8   11.3                                                                              100  0.005                                                                               90°/3 hrs                                                                   31.58                                                                              0.41                                                                              6.36   7700                          f)                                                                              10.4                                                                              9.8   --  100  0.1  105°/3 hrs                                   __________________________________________________________________________     *Yield in grams.                                                         

Terpolymers of the previous examples can be prepared from other alkenylaromatic monomers than styrene or mixtures thereof with styrene.Likewise maleic anhydride may be replaced by any of the anhydridespreviously mentioned or mixtures thereof. Various vinyl benzyl ethermonomers may also be used. The mole ratios in the terpolymer of theanhydride/aromatic monomer/vinyl benzyl ether may vary from 1/0.75/0.25to 1/2.99/0.01, respectively. Terpolymers with styrene and maleicanhydride are preferred. The above described terpolymers are excellentthickening agents for latex paints.

U.S. Pat. Nos. 2,921,930 and 3,301,829 propose to modify astyrene-maleic anhydride copolymer by reaction with various nonionicsurfactant alcohols to improve their thickening action. Following themethods of these patents it has been found that crosslinked products areobtained. It is known that crosslinked polymers give viscous solutions.One can make products under controlled conditions which give smoothviscous solutions, however, the viscosity, on aging, is not stable. Tocompare these products with the products of this invention the followingexample is presented.

EXAMPLE 5

An equal molar copolymer of styrene-maleic anhydride (10% MEK viscosity,8 cps) was esterfied according to U.S. Pat. No. 2,921,930 with 2.5 molepercent of a nonionic surfactant (nonyl phenol/40 EO) in MEK solvent.The polymeric ester was devolatilized and dissolved in water byneutralizing it with NaOH. Five weight percent sodium salt solutions ofthe above polymer and a copolymer of this invention (copolymer ofExample 4,d) were compared.

Viscosity Stability at 70° C

    ______________________________________                                        Time in    Example 4d      Example 5                                          Hours      (this invention)                                                                              (prior art)                                        ______________________________________                                         0            2700 cps        4800 cps                                         24        2250             950                                                48        2100             400                                               120        2000             60                                                144        2000             --                                                ______________________________________                                    

While the prior art had an initial higher viscosity, the viscosityrapidly decreased with time. The viscosity stability of the copolymersof this invention is dramatically evident.

The copolymers of this invention may be conveniently prepared, aspreviously illustrated, or by any of the other methods well known topolymer chemists. Aromatic solvents, chlorinated aromatic and aliphaticsolvents, tetrahydrofuran, dimethyl formamide, dimethyl sulfoxide,ketone solvents and the like may be used. Any convenient concentrationof monomers in the solvents may be used such as 10 to 60 weight percentbut generally a concentration of about 20 to 40 percent is used. Thetemperature may also vary considerably, but normally is about 40° to110° C. Lower temperatures generally produce higher molecular weightsand vice versa. The polymerization may be run under pressure but in mostinstances is not necessary. Catalyst concentrations usually range fromabout 0.001 to 2 weight percent based on the monomers. An inertatmosphere such as N₂, CO₂, and the like is usually employed in thepolymerization. Peroxide and other free radical generating catalysts areconveniently used.

EXAMPLE 6

Additional vinyl benzyl ether monomers may be prepared according toexample 1 from the following nonionic surfactants.

A dodecylphenoxy (ethyleneoxy)₁₄ ethanol

B tridecyloxy (ethyleneoxy)₁₄ ethanol

C stearyloxy (ethyleneoxy)₁₉ ethanol

D lauryloxy (ethyleneoxy)₁₉ ethanol

E dodecylmercapto (ethyleneoxy)₉ ethanol

F t-alkyl (C₁₈ -C₂₂) amino (ethyleneoxy)₂₄ ethanol

G dialkylamino (ethyleneoxy)₄₀ ethanol

H n-methylstearamido (ethyleneoxy)₄₀ ethanol

I n-ethyllauramido (ethyleneoxy)₃₀ ethanol

J octadecylmercapto (ethyleneoxy)₆₀ ethanol

K n-methyl-N-dodecylamino (ethyleneoxy)₄₀ ethanol

L oleyloxy (ethyleneoxy)₃₅ ethanol

M n,n-dioctylamino (ethyleneoxy)₂₅ ethanol

N hexadecylmercapto (ethyleneoxy)₄₅ ethanol

EXAMPLE 7

Using the vinyl benzyl ether monomers of examples 1 and 6 additionalpolymers within the scope of this invention are summarized below.

    ______________________________________                                        A                       C                                                     VBE     B               Optional   Mole Ratio                                 Monomer*                                                                              Solubilizing Monomer                                                                          Monomer    A:B:C                                      ______________________________________                                        1,F     acrylic acid    styrene    .02/.5/.48                                 1,H      "               "         .01/.5/.49                                 "        "              butyl acrylate                                                                           .01/.6/.39                                 "        "              methyl     .02/.6/.38                                                         methacrylate                                          1,G      "              styrene    .02/.5/.48                                 1,B     ethyl acid maleate                                                                             "         .02/.5/.48                                 1,H      "               "         .02/.5/.48                                 "       ethyl acid fumarate                                                                            "         .02/.5/.48                                 "       hydroxyethyl acrylate                                                                          --        .01/.99/--                                 "       sodium styrene sulfonate                                                                       --        .02/.98/--                                 "       sulfoethyl methacrylate                                                                        --        .02/.98/--                                 "       aminoethyl methacrylate                                                                        --        .01/.99/--                                 "       methacrylic acid                                                                               --        .01/.99/--                                 "       maleic anhydride                                                                              isobutylene                                                                              .01/.5/.49                                 "        "              vinyl methyl                                                                             .01/.5/.49                                                         ether                                                 "        "              vinyl toluene                                                                            .02/.5/.48                                 6,B      "              styrene    .01/.5/.49                                 6,C      "               "         .01/.5/.49                                 "       acrylic acid     "         .01/l5/.49                                 6,E     maleic anhydride                                                                               "         .01/.5/.49                                 6,J      "               "         .01/.5/.49                                 6,H      "               "         .01/.5/.49                                 6,F      "               "         .01/.5/.49                                 1,H     vinyl pyrrolidone                                                                              "         .01/.5/.49                                 "       itaconic acid    "         .01/.5/.49                                 ______________________________________                                         *Number refers to example number and the letter refers to the monomer of      that letter in the example                                               

EXAMPLE 8

An acrylic latex (Rhoplex AC 35) was formulated into a paint as follows:

    ______________________________________                                        Pigment Grind         lbs/100 gals.                                           ______________________________________                                        Water                 125                                                     Dispersant (Tamol 731)                                                                              8                                                       Polypropylene glycol (1200 M.W.)                                                                    8                                                       Preservative          2                                                       Titanium Dioxide      200                                                     CaCO.sub.3            257                                                     Ethylene glycol       15                                                      Surfactant (Triton X-100)                                                                           5                                                       Paint Let Down                                                                Rhoplex AC35 (46% solids)                                                                           387                                                     ______________________________________                                    

Storage stability tests were made with the above paint thickened with acopolymer of this invention similar to polymer (e) in Table I and astyrene-maleic anhydride ester similar to the one of example 5 except 5mole percent of nonionic surfactant was esterified rather than 2.5 molepercent.

    ______________________________________                                                         SMA      VBE                                                                  ester    polymer                                             ______________________________________                                        Lbs. thickener/100 gal.                                                                           4          4                                              Paint Viscosity, K.U.                                                                            106        105                                             Viscosity after aging                                                         at 120° F                                                              1 week             102        109                                             2 weeks            90         108                                             3 weeks            84         107                                             4 weeks            76         107                                             ______________________________________                                    

What is claimed is:
 1. A polymer comprising(a) about 0.2 to 15 molepercent of a vinyl benzyl ether monomer having the formula ##STR11##wherein R is hydrogen or methyl, m is about 10 to 100 and Y is --SR₁,##STR12## where R₁ is an alkyl, aralkyl or alkaryl hydrophobic group of10 to about 22 carbon atoms, R₂ is an alkyl group of 1 to about 22carbon atoms and R₃ is hydrogen or an alkyl group of 1 to about 22carbon atoms, provided R₂ and R₃ in combination have at least 10 carbonatoms. (b) the balance to make 100 mole percent of one or morecopolymerizable ethylenically unsaturated monomers provided a watersolubilizing amount of at least one monomer having a carboxylic acidgroup, an anhydride group, a sulfate group, a sulfonate group or ahydroxyl group is present.
 2. The polymer of claim 1 wherein m is 10 toabout
 40. 3. The polymer of claim 1 wherein the mole percent of saidether monomer is about 0.2 to 5 percent.
 4. The polymer of claim 1wherein the mole percent of said ether monomer ranges from about 1 to 3percent.
 5. The polymer of claim 1 wherein the oxyalkylene group isoxyethylene.
 6. The polymer of claim 5 wherein m is 10 to about
 40. 7.The polymer of claim 5 wherein the mole percent of said ether monomer isabout 0.2 to 5 percent.
 8. The polymer of claim 5 wherein the molepercent of said ether monomer ranges from about 1 to 3 percent.